Recently, there is known a Software-Defined Networking (SDN) that can cause a controller to automatically and rapidly control resource setting of a NetWork (NW) in accordance with an NW use request of a user, a use situation of the NW, etc. The SDN controller dynamically assigns resources on demand in accordance with a service request of a user for a communication service to provide the communication service to the user by using the resources. Moreover, when the communication service for the user is terminated, the SDN controller releases the resources at once, and assigns the unoccupied resources to another user. As a result, the SDN can improve the use efficiency of resources, and thus, the facility cost and the operational cost can be reduced.
Moreover, recently, a Virtual Network Operator (VNO) or a Mobile Virtual Network Operator (MVNO) increases, which borrows an NW facility from a network operator or a mobile network operator to provide a communication service to a user. For example, when a Network Service Provider (NSP) borrows an optical access line from a network operator having an optical access network, the NSP can provide, as a VNO, an optical access line service to a user. On the other hand, when an NSP borrows a wireless communication facility from a mobile network operator having a mobile phone network, the NSP can provide, as an MVNO, a mobile communication service to a user.
Hereafter, an NSP increases, which borrows resources from a network operator employing an SDN technology. An SDN controller fixedly assigns resources in an NW to the NSP. As a result, the NSP can provide a communication service to a user of the NSP by using the resources borrowed from the network operator.    Patent Literature 1: Japanese Laid-open Patent Publication No. 10-078931    Patent Literature 2: Japanese Laid-open Patent Publication No. 2012-190109
However, because the SDN controller fixedly assigns a resource in an NW to each NSP, the resource in the NW is not be shared between the NSPs, and thus the use efficiency of the resource is not sufficient.